The currently known applicators of pharmaceutical or therapeutic substances comprise various setting mechanisms for setting an amount of a substance to be dosed. Some of these mechanisms enable reducing the set dose. A number of examples of these types of mechanisms will be discussed below. Dosing devices are typically devices for injecting (called injectors). Some of these devices are provided with a housing resembling a pen (called pen injectors).
A European patent EP1351732B1 discloses a device for setting a dose for use with a reservoir filled with a liquid, wherein the device for setting the dose is adapted for repetitive injection of individually set liquid doses from the reservoir. The device comprises a housing, a driving element, spring means, dosing assembly and releasable lock means coupled with the housing for holding the device in a set position regardless of the operation of the spring means.
A European patent EP1926514B1 discloses an injecting device comprising a housing with a reservoir for a product to be injected, a drive knob, which, after setting a product dose, can be moved with respect to the housing in a direction in which it increases the dose, and in a direction providing a correction of the dose, a delivery (delivering) element for emptying the set dose, a slipping clutch with a detent element and a counter detent element, which come into mutual positive and non-positive engagement in discrete latching positions of the housing to arrest the actuating head during a movement in the dose setting direction or in the dose correcting direction, and a spring element, which applies a spring force opposing the movement of the actuating head in at least one direction.
A Polish patent PL211266B1 discloses a dose correction mechanism of an automatic applicator, comprising a double-clutch assembly for setting and correcting the set dose, constituting a coupling sleeve connected with a ratchet sleeve and connected with a nut, wherein the coupling sleeve is coupled radially with the ratchet sleeve by a control recess and a projection and coupled with a driving nut by latching arms passing through through-holes of the coupling sleeve.
A PCT application WO2006/045526 discloses a dial-down mechanism for an injection device comprising a torsion spring for assisting injection of a dose of medicament from the injection device, the dial-down mechanism comprising dial-up cam arranged to receive and engage with a dial-up key, wherein the dial-up cam and the dial-up key are adapted to, upon rotation of a dose setting member in a first direction, cooperate to strain the torsion spring of the injection device, and a dial-down cam arranged to receive and engage with a dial-down key.
A US patent application US2015112274A1 discloses a medication injection pen, comprising a housing; a dose set knob rotatable with respect to said housing; a brake assembly disposed in said housing and having a ratchet member; and a driver including at least one external tooth engaging said ratchet member, wherein said engagement between said ratchet member and said at least one external tooth substantially prevents said driver from rotating with respect to said dose set knob during dose setting and dose correcting, and said engagement between said ratchet member and said at least one external tooth allows said driver to rotate with said dose set knob during an injection.
A PCT application WO2014033195 discloses a reusable device for delivering a drug, for selecting and dispensing a number of user variable doses of a medicament, comprising a housing, a cartridge holder, a piston rod, a driver, a display member for indicating a set dose, a clutch and a button.
A PCT application WO2015055640 discloses a drug delivery device comprising a cartridge comprising a cylindrical body portion, an outlet portion and an axially displaceable piston, an expelling assembly, a rotatable driver assembly allowing a user to set a dose amount to be expelled and strain the drive spring correspondingly, a ratchet allowing the driver assembly to be rotated from an initial position in a first direction and held in a rotational position corresponding to a set dose.
There is a need to improve the known devices to eliminate at least part of the problems as described above and to provide alternative solutions. The problems present in the devices known so far include, among others: a large number of elements, highly complicated design, high manufacturing costs, insufficient durability, a relatively low strength (in particular, elements that are fragile and brittle during manufacture and use), insufficient dosing accuracy, problems with uncontrolled outdropping of the substance, and insufficient operating comfort for a user. Not all solutions meet technological manufacturing regimes, and they do not ensure patient safety during use. Moreover, in case of mechanisms based on a number of cam-and-wedge couplings, in relation to small-dimension devices, e.g. injection devices, it has been shown that such cam-and-wedge elements of small dimensions are not reliable—they tend to break during manufacture or during use.
In the known devices, forces required to set and correct the dose are different, in particular the force needed to reduce (correct) the dose is greater than the force to set the dose. Furthermore, the forces can increase substantially along with increasing the set dose. Some solutions require a ratchet as an element necessary for operation. Other solutions do not have a driving spring, and are not automatic.
Therefore, there is a need to provide a mechanism, which would solve at least part of the above-mentioned problems and achieve at least partially the following effects: lower number of elements, greater design simplicity, lower manufacturing costs, desirable strength during manufacture and use, reliability, desirable durability, desirable dosing accuracy (in particular, complying with ISO 11608-1:2014), little outdropping, desirable operating comfort for a user, ease of operation, small resistance during dose setting and/or dose correcting, providing substantially equal force during dose setting and correcting, a mechanism devoid of a ratchet or cams, providing a possibility of cooperation with spring means for effecting a movement of a piston rod, providing automatic dose supply and requiring a smaller force from a user.
There is also a need to provide an improved method for delivering substances, in particular pharmacological substances, in particular using the mechanism as disclosed herein.